Entries in Hungary
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Photo Courtesy - Getty Images(NEW YORK) -- Western Hungary still is digging out from under 24.7 million cubic feet of caustic red sludge -- a toxic tide unleashed when a containment pond at an old aluminum factory gave way. The breach killed nine, injured 150, forced home evacuations and ruined property over a 15.6 square mile area.

Hardly had the mud subsided, though, when an environmental group fingered another 150 industrial sites in the Danube region, each a potential disaster in the making. Here in the U.S., what industrial dangers lie in wait? Experts suggested this list of the most unsavory possibilities to ABC News:

Manure Lagoons

"Manure lagoon" may sound like the title of a Captain & Tennille hit single; but the phrase in fact describes impoundments of animal waste in liquid form on cattle, hog, dairy or chicken farms. These can contain millions or even tens of millions of gallons of excrement. Dams designed to contain the waste have on occasion failed.

There is concern about lagoons on hog farms in North Carolina and Iowa, as well as on dairies in California and Texas, says Newell, who adds that these pools are a nationwide problem.

Chlorine Gas

"It's not like you go to sleep and die painlessly. It's a horrible death." Rick Hind, legislative director for Greenpeace, is talking about what happens when you inhale chlorine gas, used widely in water treatment and the plastics industry. "It reacts with any liquid to turn into hydrochloric acid. You die of pulmonary edema. Your lungs melt and you drown in the fluid of your lungs."

Industrial Worm

Stuxnet -- a computer worm more sophisticated and potentially more destructive than any previously discovered -- has been attacking industrial facilities for about a year. Who made it and why remain a mystery, but security professionals regard it as so extraordinarily complex that it could only be the work of a nation-state or a sophisticated, well-financed private group.

The worm enters Windows-based industrial control systems of factories, chemical plants, power plants and transmission systems by way of a corrupted memory stick and is thought to do such things as change autonomously the speed of pumps and other equipment, thus creating dangerous situations of over-pressure or under-pressure. It doesn't need human guidance to work its mischief.

Pipeline Blasts

The explosion that leveled a San Bruno, California, neighborhood in September -- sending flames 300 feet into the air -- wasn't the first and likely will not be the last conflagration caused by a ruptured natural gas pipeline (in this case, one belonging to the Pacific Gas & Electric Company).

The age of a pipeline matters less than inspection and maintenance. So says Carl Weier, head of the Pipeline Safety Trust, a government-financed watchdog group. "Most of the pipelines in this country are 40 to 50 years old. If properly maintained, they don't present a danger." However, even a new pipeline, he says, will go to failure if not well inspected and maintained.

Photo Courtesy -- Getty Images(NEW YORK) -- The toxic red sludge that engulfed the streets of a Hungarian town this week appears almost alien, but toxic waste is a very real threat for millions of people in the United States.

Coal ash, a byproduct of coal power plants, is stored in largely unregulated dumps across the country, and retaining walls holding in the toxic material occasionally give way.

A large coal ash spill near Kingston, Tenn. destroyed homes and scarred the environment in a 300-acre area in December 2008.

The coal ash contains heavy metals such as lead and mercury that potentially can cause birth defects, cancer and other health problems.

Just last week, there was a much smaller coal ash spill in Wilmington, N.C. The breached pit didn't present a threat to the public, but it served as a fresh reminder of the standing pools of ash that remain nationwide.

While the federal government does not consider coal ash a hazardous material, plenty of other toxic dumps are being tracked by authorities.

The federal government's Superfund program was enacted in 1980 by President Jimmy Carter, charged with identifying uncontrolled hazardous waste sites around the country.

Three decades later, there are 1,282 active sites on the "National Priorities List," the government's short list of Superfund sites so hazardous that they merit long-term clean up.

NPL sites dot every state in the nation, located in both major population centers and rural areas, with hundreds of millions of Americans living nearby.

Sites can be found everywhere from densely populated Brooklyn, N.Y., where the Gowanus Canal contains dangerous pollutants, to Conroe, Texas, where chemicals from a wood-treating facility leeched into the groundwater.